package UDP;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;

//回显服务器
public class UdpEchoServer {
    private DatagramSocket socket = null;

    public UdpEchoServer() throws SocketException {
        //服务器需要固定端口号
        this.socket = new DatagramSocket(9090);
    }

    public void start() throws IOException {
        System.out.println("服务器启动");

        while (true) {
            //接收请求
            DatagramPacket requestPacket = new DatagramPacket(new byte[4096], 4096);
            socket.receive(requestPacket);

            //将请求转化为字符串
            String request = new String(requestPacket.getData(), 0, requestPacket.getLength());

            //根据请求计算响应
            String response = process(request);

            //发送请求

            //根据请求的IP与端口号来发送
            DatagramPacket responsePacket = new DatagramPacket(response.getBytes(),
                    0, response.getBytes().length, requestPacket.getSocketAddress());

            socket.send(responsePacket);

            //打印日志
            System.out.printf("[%s, %s] : request : %s, response : %s\n", requestPacket.getAddress().toString(),
                    requestPacket.getPort(), request, response);
        }
    }

    private String process(String request) {
        return request;
    }

    public static void main(String[] args) throws IOException {
        UdpEchoServer udpEchoServer = new UdpEchoServer();
        udpEchoServer.start();
    }
}
